1. Field of the Invention
The present invention relates to a high frequency semiconductor switch, and more particularly, to a high frequency semiconductor switch used in wireless communications apparatuses.
2. Description of the Related Art
A front end of wireless communications apparatuses such as mobile phones, PCs, and the like, has had a high frequency semiconductor switch mounted therein. The high frequency semiconductor switch switches a path along which a signal received from an antenna is transferred and a path along which a signal transmitted from the antenna is transferred. To facilitate switching, the high frequency semiconductor switch includes a plurality of field effect transistors (FETs).
The FETs are connected to a transmission terminal to which a transmission signal is input, or a reception terminal from which a receiving signal is output. When a signal is transmitted, voltage is applied to a gate of the FET connected to the transmission terminal and when a signal is received, voltage is applied to the gate of the FET connected to the reception terminal, such that a signal transfer path is formed.
As the FET, a comb transistor has been known in the art (for example, see Patent Document 1: Japanese Patent Laid-Open Publication No. 11-103072). The comb transistor has a structure in which a source wiring connected to a source region and a drain wiring connected to a drain region have comb shapes, and comb teeth are disposed to the left and right to be alternately engaged with each other, when viewed from above. The gate is formed to be a comb gate, and the source wiring and the drain wiring may be disposed to be parallel with the teeth.
However, in the above-mentioned comb gate, the comb teeth portions extend for a distance equal to or longer than the source region and the drain region. In this case, voltage may fall due to a resistance component of the lengthwise extended gate and as a result, adequate voltage distribution may not be obtained. As a result, insertion loss characteristics and harmonic characteristics may be deteriorated.